Load-bearing characteristics and energy evolution of fractured rock masses after granite and sandstone grouting

Abstract

Experiments on grouting-reinforced rock mass specimens with different particle sizes and features were carried out in this study to examine the effects of grouting reinforcement on the load-bearing characteristics of fractured rock mass. The strength and deformation features of grouting-reinforced rock mass were analyzed under different loading manners; the energy evolution mechanism of grouting-reinforced rock mass specimens with different particle sizes and features was investigated; the energy dissipation ratio and post-peak stress decreasing rate were employed to evaluate the bearing stability of grouting-reinforced rock mass. The results show that the strength and ductility of granite-reinforced rock mass (GRM) under biaxial loading are higher than that of sandstone-reinforced rock mass (SRM) under uniaxial loading. Besides, the energy evolution characteristics of grouting-reinforced rock mass under uniaxial and biaxial loading mainly could be divided into early, middle, and late stages. In the early stage, total, elastic, and dissipation energies were quite small with flatter curves; in the middle stage, elastic energy increased rapidly, whereas dissipation energy increased slowly; in the late stage, dissipation energy increased sharply. The energy dissipation ratio was used to represent the pre-peak plastic deformation. Under uniaxial loading, this ratio increased as the particle size increased and the pre-peak plastic deformation of grouting-reinforced rock mass became larger; under biaxial loading, it dropped as the particle size increased, and the pre-peak plastic deformation of grouting-reinforced rock mass became smaller. The post-peak stress decline rate A_v was used to assess the post-peak bearing performance of grouting-reinforced rock mass. Under uniaxial loading, parameter A_v exhibited reduction as the particle size kept increasing, and the ability of post-peak of grouting-reinforced rock mass to allow deformation development was greater, and the bearing capacity was greater; under biaxial loading, A_v increased with the particle size, and the ability of post-peak of grouting-reinforced rock mass to allow deformation development was low and the bearing capacity was reduced. The findings are considered instrumental in improving the stability of the roadway-surrounding rock by granite and sandstone grouting.

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